求助， ubuntu 下 pip 安装 virtualenv 报错

本心python新手，实在是没辙了，才来讨扰各位大神，清看在今天周五心情好的份上，救救小弟一把吧。得到的错误信息如下：
Exception:
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 122, in main
status = self.run(options, args)
File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 283, in run
requirement_set.install(install_options, global_options, root=options.root_path)
File "/usr/lib/python2.7/dist-packages/pip/req.py", line 1435, in install
requirement.install(install_options, global_options, *args, **kwargs)
File "/usr/lib/python2.7/dist-packages/pip/req.py", line 671, in install
self.move_wheel_files(self.source_dir, root=root)
File "/usr/lib/python2.7/dist-packages/pip/req.py", line 901, in move_wheel_files
pycompile=self.pycompile,
File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 206, in move_wheel_files
clobber(source, lib_dir, True)
File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 193, in clobber
os.makedirs(destsubdir)
File "/usr/lib/python2.7/os.py", line 157, in makedirs
mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/dist-packages/virtualenv-13.0.1.dist-info'

Storing debug log for failure in /home/qq/.pip/pip.log